package algo;

import java.util.*;

public class sample7 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
	int A = Integer.parseInt(Integer.toBinaryString(sc.nextInt()));
	int C = Integer.parseInt(Integer.toBinaryString(sc.nextInt()));
	int B = 0;
	B = A ^ C;
	System.out.println(Integer.parseInt(Integer.toString(B), 2));
	}
}